Time resolution of Ge avalanche photodiodes operating as photon counters in delayed coincidence

Abstract

The application of Ge avalanche photon counters for fast light detection in the energy range 0.7<hν<1.1 eV is investigated. Individual photons cause discrete self‐sustaining avalanche pulses in alloyed Ge diodes, slightly biased above breakdown voltage at 77 K. The shape of short light pulses (τ=1 nsec) was determined by a delayed coincidence method, which accumulates the distribution of delay times between a light pulse and the following microplasma pulse. It is shown in a quantitative model that the time response of the detector is determined by minority carrier diffusion. Germanium avalanche diodes operating as photon counters with a delayed coincidence technique are suitable for detection of very short light pulses at low levels, and the shapes of fast signals can be detected despite relative long time constants of the detector. In order to reduce the necessary integration times, signal repetition rates up to ∼100 kHz can be used.